When Comair Flight 5191 took off from Blue Grass Airport in Lexington, Ky., it was flying low--low enough to clip a boundary fence and immediately crash. The reason was hard to accept: The pilot picked the wrong runway, one that was too short for commercial flights. Whether he was misdirected by the control tower or simply didn't notice is unclear. Couldn't a simple cockpit navigation system, similar to GPS systems that alert drivers when they're heading the wrong way, have averted the biggest U.S. air disaster in five years?

The Airport Moving Map program displays a real-time map on a cockpit screen, pinpointing the plane's current location at the airport.
NASA's air-safety database lists two incidents since 1993 in which pilots were confused by the runway configuration at Blue Grass. Neither incident ended in a crash, but the need for a better airport navigation system should have been clear.

The tools used by most pilots to find their way around airports are surprisingly antiquated--a magnetic compass and a paper diagram. Planes equipped with digital maps of airports and terrain, on screens called electronic flight bags (EFBs), are extremely rare. Comair 5191--a CRJ-100 commuter jet--did not have an EFB.

EFBs have been around for years, and Colorado-based map data company Jeppesen provides updated airport maps every few weeks. Jeppesen also makes Airport Moving Map, an EFB application that shows a plane's location in relation to the taxiways and terminal buildings. But for now, only a limited number of Boeing 777s are outfitted with EFBs, let alone the new software.

So why aren't EFBs more common? Many airlines, already struggling with bankruptcy, balk at the cost. "Look at the number of airlines operating airplanes that are 30 to 35 years old," says Eric Anderson, a spokesman for Jeppesen. "Is it a good business decision to retrofit airplanes when they're going to be retired soon?" The FAA rarely mandates equipment that airlines can't afford, and only a few companies, such as UPS, are voluntarily updating their existing fleets. And while Boeing 787s and Airbus 380s will incorporate EFBs, experts expect a 10- to 15-year wait before airlines replace their fleets and finally make the technology standard issue.